Pictogram (象形); derived from the pictogram of a horse with its head turned to look back and showing a flowing mane in the wind. The four short strokes at its base (灬) represent its feet, and the sweeping hook stroke in the lower right represents its tail.

Compare also 鳥 ‎(“bird”), whose current form is similar (graphically, 灬 for claws/legs).

Contrast with 鹿 ‎(“deer”), which saw a very different development, and 𢊁 ‎(“bison”) (as in 薦), which is a hybrid: it has the the legs of 馬 (灬) but the head of 鹿.

From Old Japanese.[1] Recorded in the Nihon Shoki as having been brought over from the Korean peninsula kingdom of Baekje, with the earlier reading of ma. The initial m sound was apparently emphasized,[1][2] possibly similar to *mma, becoming then uma or muma, via processes also seen in the word 梅 ‎(ume, mume, “plum”).

The ma sound denoting "horse" is common to a number of languages of central Asia, where horses were first domesticated, suggesting a possible cognate root. Compare Manchuᠮᠣᡵᡳᠨ ‎(morin, “horse”), Mongolморь ‎(morj, “horse”), Korean말 ‎(mal, “horse”), Mandarin馬 ‎(mă, “horse”), and Proto-Indo-European *mark(')- ‎(“horse”) and descendants such as Irishmarc ‎(“horse”, archaic) or Englishmare ‎(“female horse”). More at *mark(')-.